MARCH
1960
319
CYCLIC ACROLEIN ACETALS
[CONTRIBUTION FROM SHELL DEVELOPMENT COMPANY]
Cyclic Acrolein Acetals R. F. FISCHER
AND
c. W.
SMITH
Received October $7, 1959
Acetals have been made in 70-98% yields by reaction of acrolein and various alcohols, largely 1,2- and 1,8glycolS. 0Chloro-, hydroxy-, cyano-, and a,p-epoxy-derivatives otherwise difficultly accessible are readily prepared from the acetals derived from 2-methyl-2,4pentanediol or pentaerythritol.
Acrolein contains two highly reactive groups, an aldehyde and an ethylenic linkage. Numerous examples of addition to both the carbonylic and ethylenic functions are known.’ Early attempts to form unsaturated acetals led to mixtures in which extensive addition to the double bond occurred.2 Recently, however, a number of publications have indicated that in acidic media the carbonylic function is slightly more reactive toward alcohols than is the ethylenic group and in particular that substituted 1,2- and 1,3-glycols tend to form cyclic acetals. Schulz and Wagner3 prepared 3,g-divinyl2,4,8,10-tetroxaspiro-(5,5)-undecane(diallylidenepentaerythritol), I, from pentaerythritol and a large excess of acrolein, 0-CHz CH-CH-CH
//
\c/
CHz-0
\
CH-CH=CHz
minimizing addition to the olefinic bond; 2) 1.2or 1,3-glycols should be used, as they lead to the more stable cyclic acetals; 3) glycols substituted on the hydroxyl-bearing carbons are preferred, as such substitution favors ring formation while hindering addition to the ethylenic bond. A number of representative acrolein cyclic acetals have been prepared in 70-98% yield. In most cases distillation without fractionation from the reaction mixture has given products with analyses in agreement with the theoretical values. The products from 1,2-glycols are 2-vinyl-l,3-dioxolanes. 411, while from 1,3-glycols one obtains 2-vinyl-1 ,:
